Do you just put the tester in the spark plug hole and fire it over. Or do I need to plug something. My new motor (( Internal Combustion Engine ? )) went caput today. Two hours on it. Never over half throtle. Synthetic oils and ER additive. NEver got over a 1000 degrees. If I am doing it right I only got 60 psi. It was running good and just died. Plug looked fine too.

J

You buy a compression tester that screws into the spark plug hole then you
hold the throttle wide open and crank the Engine over until it quits building
compression.

What kind of Engine?

What is the history why the rebuild?

Testor goes in the plug hole, hold the throttle open, crank it several times untill it get to maximum reading, then tell Hoser what the reading is, he is the most likely to know what is happening.

I am assuming this is a single cylinder machine, with multiple cylinders, you simply repeat the proceedure on each cylinder. But, be sure to disconnect the plug wires so is doesn't start running.

Depending on what Engine you have, and what altitude you are at, the readings might go anywhere from 120 to 185 on a good cylinder. Hipo two strokes will read higher that stock, and (I think) four strokes will show lower readings, at least on average.

If this is an FL350 or 400, you should be getting readings in the mid 100s, if the cylinder is good.

Hoser is also going to want pictures of the intake and exhaust ports, pull the carb boot and exhaust pipe off and take pictures if at all possible, and, if possible, take the photos out doors in good light.

Don't take the head off yet.....

What you are looking for is scoring or burn marks, look also for metal particles. If you do have any of the preceeding, you are headed for a tear down, but most important, is to get the compression and photos.

Good luck!!

could be a few different reasons for the loss of commpression .on the fl 350 compression should be around 140-155 lbs.depending on the head gasket thickness and new piston,rings and bore.
did you make sure the bottom end was completely spotless of debris from the last siezure.
I also never use synthetic oils for break-in.

Fl350 Engine I sent to Randy at OS. motor (( Internal Combustion Engine ? )) was torn down and completely rebuilt from the bottom up. I followed Randy's instructions to the T. Put one size larger jet in it. Mix the oild and gas like recommended and was just screwing around and never more then a little over half throttle. Paid around 1500 for this rebuild and am sure dissapointed I only got two hours out of it since the old motor (( Internal Combustion Engine ? )) was prob ten years since rebuild and I ran the piss out of it at around 1200-1250 degrees until the tired ole hen let go after a year and a half. I even had them pre-run it and re torque all the bolts.

Wow that sux...


Do the autopsy and see what is what, start with the compression test it should be what
it was before you started it for the first time, if compression is low then pull the exhaust
and look at the piston check for scoring, if it is scored then you need to pressure test
the Engine to ensure it does not have an air leak before you take it apart, you also
want to carefully remove the carb and see how much fuel is in the float maybe it
was starved for fuel.. Many things can cause them to stick.

What happen before that promt you to rebuild the Engine?

randy did the break in ?

Carb had mucho fuel in the bowls. Randy pre ran it on a stand for 15 min then retorqed everything. Not blaming them just pissed it bit the dust so fast. Got motivated this evening and once the exhaust came off I saw were the top portion of the piston snapped off in the corner. I ran it twice for 15 min idle and then my first run was for about 20 minutes the one day before my nifty radiator hosed me with water and gave me the burns on the other page. It never got hot just crappy fittings. I noticed when I tried to crank it for a buddy of mine yesterday the starter would not turn over. I thought my battery was toast. It would pull start with a great tug though "thought hmm great compression". Well I guess it had already started muffing up. After it stopped on me in the feild the starter suddenly worked great. Like I said it never got over 1000 degress I have my EGT marked and have been watching it very carefully, the plug looks good and oily too. Hell I don't know but this is very frustrating. Heres the pics.

Looked like there was a little hitch were it was ported on the exhaust too. I never heard it detonating or anything. GRRRRRRRRRRRRRRRRRRRRrr. I had them do the works, mild port job, water cooled head, reed spacer and reed kit, crank rebuild, new rod and bearings, leak down and everything. Heck I even paid for the pre run and retorq. I hate it that they had it for a little over two months and then I get stoked about putting it in and finally knowing the motor (( Internal Combustion Engine ? )) was rebuilt and kablewy.

Looks like detonation, ignition or fuel related?

Start reading http://pilotodyssey.com/Fuel-Squish-Detonation.htm

So could it have still been running lean even though the EGT never got up that high. I think I am figuring out the cuase.